Louis Tomlinson‘s sister Felicite, an aspiring fashion designer, has died aged just 18 of a suspected cardiac arrest.

Felicite, an Instagram influencer with over 1 million followers, died at her flat in London on Wednesday (March 13), as BBC News reports.

“A female believed to be aged 18 was pronounced dead at the scene,” reads a statement by Scotland Yard. “A post-mortem examination will take place in due course.”

Louis has reportedly cancelled a planned appearance at Comic Relief this evening. According to The Sun the death is being treated as “unexplained” at this stage.

Figures and friends of Tomlinson have offered messages of condolence, including James Corden, Charlie Puth and Rak-Su.

Such incredibly sad news today. You’re not on your own in this @Louis_Tomlinson So many people are pulling for you and your family right now x

— James Corden (@JKCorden) March 15, 2019

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Prayers to Louis Tomlinson. I can’t imagine how hard it is right now. Love to you brother I’m so sorry and my prayers are with you.

— charlie puth (@charlieputh) March 15, 2019

Our condolences and prayers go out the @Louis_Tomlinson and his family at this time

— Rak-Su (@RakSuMusic) March 15, 2019

The siblings lost their mother to leukaemia in 2016. It was the subject of a new single by Louis released earlier this month, ‘Two Of Us‘.

According to The Sun, a family source said: “Felicite was an absolutely adored young woman who was loved by Louis and her whole family. They are all totally devastated, as you can imagine. She had so many friends and was such a positive happy person. It’s a massive loss to the world. She was a loveable, caring, bright, passionate, popular and beautiful young lady.”